<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <link rel="stylesheet" href="./css/index.css" />
  <title>记事本</title>
</head>

<body>

  <!-- 主体区域 -->
  <section id="app">

    <!-- 输入框 -->
    <header class="header">
      <h1>小黑记事本</h1>
      <input v-model="todoName" placeholder="请输入任务" class="new-todo" />
      <button @click="add" class="add">添加任务</button>
    </header>

    <!-- 列表区域 -->
    <section class="main">
      <ul class="todo-list">
        <li class="todo" v-for="(item, index) in list" :key="item.id">
          <div class="view">
            <span class="index">{{ index + 1 }}.</span> <label>{{ item.name }}</label>
            <button @click="del(item.id)" class="destroy"></button>
          </div>
        </li>
      </ul>
    </section>

    <!-- 统计和清空 → 如果没有任务了，底部隐藏掉 → v-show -->
    <footer class="footer" v-show="list.length > 0">
      <!-- 统计 -->
      <span class="todo-count">合 计:<strong> {{ list.length }} </strong></span>
      <!-- 清空 -->
      <button @click="clear" class="clear-completed">
        清空任务
      </button>
    </footer>

  </section>

  <!-- 底部 -->
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    // 添加功能
    // 1. 通过 v-model 绑定 输入框 → 实时获取表单元素的内容
    // 2. 点击按钮，进行新增，往数组最前面加 unshift
    const app = new Vue({
      el: '#app',
      data: {
        todoName: '',
        list: [
          { id: 1, name: '跑步一公里' },
          { id: 2, name: '跳绳200个' },
          { id: 3, name: '游泳100米' },
        ]
      },
      methods: {
        del(id) {
          // console.log(id) => filter 保留所有不等于该 id 的项
          this.list = this.list.filter(item => item.id !== id)
        },
        add() {
          if (this.todoName.trim() === '') {
            alert('请输入任务名称')
            return
          }
          this.list.unshift({
            id: +new Date(),
            name: this.todoName
          })
          this.todoName = ''
        },
        clear() {
          this.list = []
        }
      }
    })

  </script>
</body>

</html>